Datasheet

1. General description
The PCF8523 is a CMOS
1
Real-Time Clock (RTC) and calendar optimized for low power
consumption. Data is transferred serially via the I
2
C-bus with a maximum data rate of
1000 kbit/s. Alarm and timer functions are available with the possibility to generate a
wake-up signal on an interrupt pin. An offset register allows fine-tuning of the clock. The
PCF8523 has a backup battery switch-over circuit, which detects power failures and
automatically switches to the battery supply when a power failure occurs.
For a selection of NXP Real-Time Clocks, see Table 57 on page 68
2. Features and benefits
 Provides year, month, day, weekday, hours, minutes, and seconds based on a
32.768 kHz quartz crystal
 Resolution: seconds to years
 Clock operating voltage: 1.0 V to 5.5 V
 Low backup current: typical 150 nA at V
DD
= 3.0 V and T
amb
=25C
 2 line bidirectional 1 MHz Fast-mode Plus (Fm+) I
2
C interface, read D1h, write D0h
2
 Battery backup input pin and switch-over circuit
 Freely programmable timer and alarm with interrupt capability
 Selectable integrated oscillator load capacitors for C
L
=7pF or C
L
= 12.5 pF
 Internal Power-On Reset (POR)
 Open-drain interrupt or clock output pins
 Programmable offset register for frequency adjustment
3. Applications
 Time keeping application
 Battery powered devices
 Metering
PCF8523
Real-Time Clock (RTC) and calendar
Rev. 6 — 17 September 2013 Product data sheet
1. The definition of the abbreviations and acronyms used in this data sheet can be found in Section 22.
2. Devices with other I
2
C-bus slave addresses can be produced on request.